High-mobility organic thin-film transistors (OTFT) were fabricated with pentacene active layers and passivated by polyvinyl acetate (PVA) in this study. The organic pentacene film showed a single phase structure with the interplanar spacing of 1.54 nm corresponding to the (001) diffraction. The initial field effect mobility of OTFT was 4.4 x 10(-2) cm(2)/Vs without the passivation. After the PVA passivation, the device exhibited an improved field-effect mobility of 1.0 x 10(-1) cm(2)/Vs. It was decreased to 8.0 x 10(-2) cm(2)/Vs after 35 days. The on/off current ratio has been at the order of 10(6). The device durability was also examined by 80 degrees bending cycle tests in tension. The transistors exhibited lower on/off ratio and higher turn-on voltage after 2500 bending cycles. The lifetime of the passivated OTFT was improved to more than 2 months in air. It has been suggested that the PVA passivation layer could effectively protect the pentacene-based OTFT from moisture and oxygen permeation. (C) 2009 Elsevier B.V. All rights reserved.